The present invention relates to a power converter.
Japanese Unexamined Patent Application Publication No. 2005-347561 discloses a power converter that includes a switching device and a capacitor and is directed to reducing parasitic line inductance. In such power converter, six insulating substrates 101 are mounted on a base plate 100, as schematically shown in FIGS. 11A and 11B. A collector pattern 102 and an emitter pattern 103 are formed on each insulating substrate 101. A switching chip 104 and a diode chip 105 are mounted on the collector pattern 102 and connected to the emitter pattern 103 by bonding wires 106. A positive conductor 107 is connected to the insulating substrates 101 by a connecting portion 107B thereof extending downward from a plate-shaped main portion 107A. Similarly, a negative conductor 108 is connected to the insulating substrates 101 by a connecting portion 108B thereof extending downward from a plate-shaped main portion 108A. The main portions 107A and 108A of the positive and negative conductors 107 and 108 are arranged one over the other and insulated from each other so as to form a laminate. Terminal portions 107C and 108C in the form of a strip are provided at the end of the main portions 107A and 108A, respectively. The terminal portions 107C and 108C are disposed adjacent to and insulated from each other. The ends of the respective terminal portions 107C and 108C form external terminals P10 and N10.
In the above-described power converter wherein a plate-shaped connecting portion is formed by bending a part of the main portions 107A and 108A, stress may be applied to the connections between the positive and negative conductors 107 and 108 and the insulating substrates 101 due to thermal deformation of the base plate 100. In such a case, the strength of the connection is lowered and the reliability of the power converter is decreased, accordingly. Specifically, the stress may be caused by difference in thermal expansion coefficient between the base plate 100 and the insulating substrate 101 under thermal cycle conditions. Alternatively, the stress may be caused by difference in the thermal expansion coefficient between the base plate 100 and the insulating substrate 101 in mounting the positive and negative conductors 107 and 108 on the insulating substrate 101.
The present invention is directed to providing a power converter in which a connection between a conductor and a base plate is less affected by thermal deformation of the base plate.